JPH01117990A - Method of extracting and utilizing geothermal energy and geothermal plant - Google Patents

Abstract

PURPOSE: To raise extracting efficiency of geothermal energy by forming penetrating passages in the bottom zone of a vertical bore hole dug deep into the ground, filling a heat-conducting substance in the passages and inserting a supply line and a return line for a heat transmission medium to flow in the vertical bore hole. CONSTITUTION: After a vertical bore hole 3 of a depth of above 1500 m is dug in a rack base 1, penetrating passages 7 formed by cracks and the like are formed surrounding the rock in a bottom zone 5 of the vertical bore hole 3. The penetrating passages 7 are formed by a blowing or the like in the bottom zone 5. A substance S with high heat-conduction is forced into the bottom zone 5. The substance S is embedded in the penetrating passages 7 and coated on the inner wall of the bottom zone 5. After that, a casing 9 with a closed end is inserted into the vertical bore hole 3 with the lower portion thereof thermally connected to a compound M including a thermal conducting substance S in proportion of appropriate amount. A return line 11 is inserted into the casing 9 to allow a heat transmission medium W to flow, so that geothermal energy can be absorbed and extracted to ground surface.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for extracting and utilizing thermal energy existing within the earth, and a geothermal plant for carrying out the method.

It is well known to extract and utilize geothermal heat in existing heat plants and heat pumps.

Existing geothermal plants extract heat from deep within the earth in the form of hot water or steam flowing through geological rock containing geothermal heat (i.e., naturally occurring hot water or steam located underground). are extracted. This can sometimes result in highly toxic condensate that poses serious environmental problems.

In heat pumps, on the other hand, it is established practice to use heat exchangers with fairly large surface areas at relatively shallow depths, and even with relatively small temperature gradients, it is a well-established practice to It is possible to obtain higher thermal efficiency. However, known heat pump devices have structural limitations, such as the relatively small surface area of contact between the heat transfer medium and the earth's interior, which is a limiting factor in the efficiency of heat pump devices. .

The purpose of the invention is to extract and utilize geothermal energy,
The purpose is to provide an improved method.

Another object of the invention is to provide a method for extracting and utilizing geothermal energy that is significantly more efficient than currently known methods.

Another object of the present invention is to provide a geothermal plant capable of implementing the above method.

The method of the invention includes the step of drilling a shaft (borehole) into the ground.

Furthermore, in the bottom region of the shaft, an intrusion passageway is formed that penetrates outward from the shaft into the surrounding rock mass. A thermally conductive material is then injected into these entry channels from the bottom region of the shaft.

Supply and return pipes for the heat transfer medium are arranged in the shaft to provide a connection between the bottom region of the shaft and the ground surface.

The heat transfer medium is moved in a closed circuit close to the bottom region of the heat exchanger or shaft and a portion of the heat is extracted before being recycled.

To achieve the desired result, the shaft should be 1.50
It is excavated underground to a depth of 0m or more. Preferably, the excavation is conducted underground to a depth of at least 5,000 m or more. In the bottom region of the shaft, entry passages are formed extending outward from the shaft into the rock mass, and these entry passages are in the form of large and small cracks and fissures.

Most of the entry passage is filled with a thermally conductive material. This significantly increases the contact area in the bottom region of the shaft compared to a shaft with a cylindrical circumference, and thus allows a large amount of heat to be extracted from the surrounding rock mass.

The hardened thermally conductive material (actually, the hardened thermally conductive material constitutes a plug in the rock where the crack has formed) is a good conductor of heat, drawing concentrated heat away from the surrounding rock. Because it absorbs heat, a large amount of heat can be transferred.

To drill a deep shaft (preferably to a depth of 1,500 m or more, e.g. 5,000 to 10,000 m deep), known drilling methods used for oil extraction from deep oil wells or for other purposes may be used. technology is used. Next, rock fragmentation by blasting, spraying of high-pressure liquids, gases or grouts (liquid mixtures of cement, sand, water, etc.), etc., is applied to the bottom area of the shaft in an area of 1,500 to 2,000 m. Cross over and invade i! Forms the ll tract. These entry channels, or fissures or fissures, are formed in addition to naturally occurring fissures or fissures.

The rock surrounding the shaft is fractured by an explosion and then washed away to form a long bottom area surrounded by an entry passage created by any of the above methods. This operation is performed upward from the bottom of the shaft, and the shaft is re-drilled each time this operation is performed.

The entry passageway is then filled with a thermally conductive material. This thermally conductive material is preferably water or cement based, with one or more of silica gel, finely ground metal powder (preferably silver and/or copper and/or aluminum powder). Added. The thermally conductive material is in fluid form and is used for pressure grouting, injected into the entry passageway and allowed to solidify.

A closed-bottom gauging is then inserted into the shaft and thermally bonded to the thermally conductive material. In particular, the bottom region of the shaft is enlarged by blasting or reaming to a larger diameter than the casing, thereby forming a roughly cylindrical underground chamber. The casing is then bonded to the surrounding rock (the entry passages of which are filled with a thermally conductive material) in a contact matrix (containing a mixture of metals and/or silicates, strongly thermally conductive materials). (preferably cement). The casing thereby forms the outer surface of the heat exchanger.

Into this casing or supply pipe a return pipe of the heat transfer medium is inserted, in the form of an inner vibrator. Unlike the supply pipe, this return pipe is open at the bottom.

The heat transfer medium is flowed downward between the inner wall of the supply pipe (gauging) and the outer wall of the return pipe, and the heat transfer medium and the rock mass in the bottom region of the shaft (which rock mass includes, as described above)
heat is absorbed by the temperature difference between the At least the upper portion of the return pipe is insulated to minimize the amount of heat lost during the rise of the heat transfer medium through the return pipe. For this purpose, at least one of special iron, asbestos cement or synthetic resin is used.

For convenience, water can be used as the heat transfer medium.

If necessary, a corrosion resistant formulation may be added to the water. The absorbed heat is transferred to the earth's surface as steam or hot water,
It is used in one of several well-known methods. When the steam is condensed, the water is reinjected into the closed circuit and returned to the shaft.

Since a given amount of heat per unit time flows through the geothermal plant, determined by the heat exchange surface area, the temperature gradient in the bottom region of the shaft and the temperature of the heat transfer medium in said bottom region, the flow rate of the heat transfer medium can be large. The more you see,
The temperature of the heat transfer medium rising in the return pipe will be lower. However, in many cases it is desirable to perform heat recovery at the highest possible temperature. To this end, according to the invention, it is provided that at least two separate shafts of the type mentioned above can be supplied and withdrawn alternately with a heat transfer medium. Therefore, a pulsating flow can be generated in the heat transfer medium. In this case, the heat transfer medium circulates in a closed circuit of one shaft, during which time the heat transfer medium is not used for heat extraction. The temperature of the heat transfer medium is therefore increased to the level required to effect efficient heat extraction. During this time, thermal energy is extracted from the heat transfer medium circulating in the other shafts. Preferably, the pressure of the heat transfer medium circulating in the idle shaft is used to determine when to activate heat extraction with the heat transfer medium.

Embodiments of the present invention will be described below with reference to the accompanying drawings.

As shown in FIG. 1a, a deep shaft (borehole) 3 is drilled in the bedrock 1 to a depth considerably greater than 1.500 m (preferably 5.000-10.00 m).

Next, as shown in FIG. 1b, an entry passage 7 is provided in the rock surrounding the bottom area 5 of the shaft 3.

The entry passage 7 into the rock consists of fissures, fissures, capillary cranks, etc., and these fissures, etc. can cause explosions (blasting) or fluid leakage in the bottom area 5. It is best formed by fracturing rock under pressure.

The explosion can be carried out, for example, by the blister method.
This can be done by slow-delayed explosion such as (Hod), and it is desirable to wash with chemicals (especially acid) after the explosion.

By carrying out such an explosion, the rock mass is relaxed in its bottom region 5 and the desired cracks and fissures are formed. Generally, this relaxation starts from the bottom of the shaft 3 and gradually rises from the lower end of the shaft to a height of, for example, 1,000 m. The rock fragments that accumulated in the shaft after the explosion were
As shown schematically in figure b, the bottom region 5 of the shaft 3 is repeatedly re-excavated by flushing out from the top with a pressure medium (preferably water). When drilling such deep shafts, it is necessary to use known techniques for drilling deep oil wells, for example.

When the cylindrical bottom region 5 reaches the required height h, as shown in FIG. 1C, there is a high thermal conductivity within the bottom region 5, as shown schematically in FIG. Substance S with properties
is injected. This substance S flows into the intrusion passage 7 which is in the open state, and fills most of the intrusion passage 7. The substance S hardens and forms a spongy heat exchange area AF.
A thermally conductive connection is formed in the axial direction of the bottom region 5. At the same time, the inner wall of the bottom region 5 is coated with a thermally conductive material S, as shown in FIG.

The thermally conductive substance S is injected as a fluid, preferably using water as a carrier. Is the thermally conductive material S entering from the top of the shaft? l? The t7 or fissure is introduced into the eye, foramen, etc.

The thermally conductive substance S is preferably composed of silica gel and finely ground metal powder made of silver and/or aluminum and/or copper.

After evaporation or impregnation of the fluid as a carrier, in the connecting or entry passage 7 and in the gap between the bottom region 5 of the shaft 3 and the outer surface of the tube of the casing 9 (FIG. 3), The almost solid thermally conductive substance S remains and diffuses into the base rock 1 like a sponge. In this way, the contact surface or heat exchange area AF between the shaft 3 and the base rock 1 surrounding it is enlarged, and the rate of heat extraction can be significantly increased.

As shown in FIG. 3, a first closed-end casing 9 is inserted into the shaft 3 which has already been treated with the thermally conductive substance S as described above. The lower end of the casing 9 must be made of a highly thermally conductive material such as metal.

By introducing a suitable compound M, the outer surface of the casing 9 in the bottom region 5 is brought into close thermal contact with the thermally conductive material S and the rock in the bottom region 5. Mixture M should consist primarily of cement and/or silica, with metal powders, metal fibers, etc. dispersed therein. This formulation M, as shown schematically in FIG.
It is injected under pressure along the outer surface of the casing 9.

FIG. 4 shows the completed shaft constructed in accordance with the requirements of the present invention. After the casing 9 has been thermally bonded to the rock surrounding it via a thermally conductive material or compound M, a return pipe 11 with an open end is inserted.

This return pipe 11 is particularly insulated in its upper region (the portion below the ground surface). This is caused by the heat transfer medium W flowing down in the annular space between the casing 9 and the return pipe 14.
This is to minimize the heat exchange occurring between the heat transfer medium W and the heat transfer medium W flowing upward in the return pipe 11. For this purpose, the return pipe 11 is either made of special steel, asbestos cement and/or synthetic resin, or is insulated with asbestos cement or synthetic resin.

The heat transfer medium W is pumped through between the inner wall of the casing 9 and the outer surface of the return pipe 11, and returns to the return pipe 1 as shown in the figure.
By rising within the Earth's interior, it serves to transport heat from the Earth's interior to the Earth's surface.

Due to the large contact surface due to the outwardly expanding entry channels 7, a considerably large amount of heat is supplied from the natural rock, the thermally conductive material S and the thermally conductive compound M to the heat transfer medium W. Ru.

The recirculation of the heat transfer medium and the extraction of heat at the ground surface are carried out using methods well known, for example in fumigation couplant district heating. As a heat transfer medium, shaft 3
Water or other low-boiling liquid is used, which evaporates in the bottom region 5 of the pump and, after extracting the available heat, condenses and flows into the closed circuit through the shaft, 3.

For the device described above, the shaft 3 prepared and equipped according to the invention forms a "geothermal furnace" with high efficiency. This geothermal furnace has a very large contact surface compared to the cylindrical surface of the shaft casing 9 itself, and therefore can extract a considerably large amount of heat from the earth per unit time and therefore from the base rock 1. A large amount of heat can be transferred to the heat transfer medium and transported to the earth's surface.

FIG. 5 shows the layout of a geothermal power plant constructed according to the present invention. This geothermal power generation plant is equipped with, for example, three geothermal utilization shafts 13a to 13c, and each shaft is preferably configured like the shaft shown in FIGS. 1 to 4. These shafts 13a-13c can be fluidly interconnected or configured to operate separately.

If the rock between adjacent shafts is formed with, for example, natural karst-like continuous intersecting channels, circulating flow can be created between the shafts by introducing a thermally conductive material from one shaft. can be established and heated liquid or steam can be extracted from the adjacent shaft. This configuration dramatically increases the amount of heat extracted from the earth compared to the embodiment that forms the first subject of the invention (i.e., the embodiment configured to recover heat separately from each shaft). can be increased. A geothermal survey has shown that a karst-like geological structure can be expected, at a depth that allows heat utilization, and/or preferably in rock with high thermal conductivity, such as granite. It is better to install a vertical shaft at the location.

In a preferred embodiment of the invention, the return pipes 15a to 15c of the heat transfer medium are connected to heat utilization units (heat extraction units) 19a, 19 through control valves 17a% 17c.
b or link the heat transfer medium to the vertical shaft 13a~
It is connected in a closed circuit to supply pipes 21a to 21c for returning directly to 13c. Control valves 17a to 17c are control unit 2
3, some of the shafts are connected to heat extraction units t-
It can be operated in a closed circuit without looping through 19a and 19b.

In this case, the temperature of the heat transfer medium increases asymptotically to a high level equal to the rock temperature in the bottom region 5 of the shaft (Fig. 1b), while in the other shaft (at the required temperature where the heat transfer medium is already available). The shaft reaching the shaft) is controlled by the heat extraction unit 19 by the control unit 23 and the control valves 17a to 17c.
a, switched to L9b. Control unit 23 can perform temperature control and/or pressure control. The temperature and/or pressure is detected in the tubes leading the heated liquid from the respective shaft, and the connection to the extraction unit) 19a, 19b takes place when the pressure and/or temperature reaches a predetermined level.

The degree of improvement when increasing the thermal conductivity of rock by injecting metal into natural openings exposed in shafts or openings created by blasting the rock can be roughly estimated based on the type of rock. It can be roughly calculated that the natural heat transfer efficiency is improved by about 2 to 10 times in the case of basalt and about 2 to 6 times in the case of granite.

The smaller value of the above magnification corresponds to the case where aluminum is used as the implanted metal, and the larger value corresponds to the case where copper or silver is used.

These or higher magnifications can be obtained near the shaft walls, but as you move away from the shaft, the magnifications decrease significantly, depending on rock conditions.

The results of these calculations will also vary depending on the volume of cracks in the rock around the shaft that can be filled with metal (grouted). By appropriate selection of the strength and duration of the explosion in the shaft, every effort can be made to create a high proportion of entry channels 7 and to have these entry channels 7 present over a wide area in a continuous network. . When the type of rock and environmental considerations permit, the surface of leaching or fractures in the rock can be enlarged or smoothed by pouring acids or other chemical solvents.

Natural hot water (hot springs) and underground steam sources (e.g. intermittent springs)
The heat transfer tubes may be provided with separators 22a to 22C at the front stage of the heat extraction unit to separate hot water and steam, as is normally done in existing geothermal plants utilizing geothermal energy. is necessary. The hot water can be transported directly for industrial, building heating, agricultural or other uses, or it can be returned back into the shaft. Separator 2
The steam removed within 2a-22c is led to pressure equalization and storage tanks (boilers) and used for power generation and/or various industrial applications.

The above-described method of utilizing thermal energy within the earth and a geothermal power plant based on the method make it possible to generate energy with high efficiency without causing significant environmental damage. Geothermal power plants built on this principle are as harmless as existing hydroelectric or thermal power plants;
From a biological point of view, they are much more beneficial than these hydroelectric and thermal power plants.

[Brief explanation of the drawing]

Figures 1a-1c schematically illustrate the three stages of excavating a shaft inside the earth and forming an entry passage outward from the bottom region of the shaft according to the invention. FIG. 2 is an enlarged schematic diagram illustrating the filling of a shaft intrusion ilI circuit with a suitable thermally conductive material in accordance with the present invention. FIG. 3 is a schematic diagram illustrating the insertion of a closed-end casing into a shaft according to the present invention. FIG. 4 is a schematic diagram illustrating the completed treatment of the shaft according to the method of FIGS. 1-3 and the provision of a heat transfer medium return pipe in accordance with the present invention. FIG. 5 is a schematic diagram illustrating a geothermal plant with multiple shafts according to the invention, which can be controlled so that heat extracted from separate shafts can be obtained substantially continuously. ■... Base bed, 3... Vertical shaft, 5...
Bottom region, 7... Entry passage 9... Casing, 11... Return pipe, 13a, 13b,
13c... Vertical shaft, 15a, 15b, 15c... Heat transfer medium, 17a, 17b, 17c... Control valve, 19
a, 19b...Heat utilization unit (heat extraction unit), 22a, 22b, 22cm...Separator, 23...
Control unit, M... compound, S... thermally conductive material, W... heat transfer medium, AF... heat exchange area. Procedural amendment (method) No. 63.11.22 1988 Director General of the Patent Office Yoshi 1) Takeshi Moon 1, Indication of case Patent application No. 183391 of 1988
No. 2, Title of the invention Method for extracting and utilizing geothermal energy and geothermal plant 3, Relationship with the case of the person making the amendment Applicant's name Hans F. Bikochi 4, agent

Claims (15)

[Claims] (1) A method of extracting and utilizing thermal energy inside the earth, which includes the steps of: (a) forming at least one shaft from the earth's surface toward the interior of the earth; (b) outward toward the earth; treating the bottom region of the shaft to form an extending entry passage; (c) forcing a thermally conductive material into the entry passage; and (d) connecting the ground surface to the bottom region of the shaft. (e) providing at least one supply and return pipe for passing a heat transfer medium for heat transfer between the heat transfer medium and the heat transfer medium; (f) discharging a portion of the heat transfer medium from a portion of the heat transfer medium before recycling the heat transfer medium through the supply pipe and the return pipe towards and from the bottom region; 1. A method for extracting and utilizing thermal energy inside the earth, comprising the step of extracting heat at the surface. (2) The method according to claim 1, characterized in that the shaft is excavated underground to a depth of 1,500 m or more. 3. The method of claim 2, wherein the shaft is excavated into the ground to a depth of at least 5,000 m. 4. The method of claim 1, further comprising treating the bottom region of the shaft to form an entry passageway extending outwardly from the bottom region. 5. The method of claim 4, further comprising flushing the relaxed bottom region with pressurized fluid. 6. The method of claim 4, further comprising treating the bottom region with a chemical to enlarge the entry passageway. (7) A fluid thermally conductive substance is injected into the entry passage from the bottom region.
The method described in. (8) The thermally conductive substance comprises water, cement and at least one of the following substances: (a) silica gel; (b) finely divided particles preferably consisting of silver and/or copper and/or aluminum; 8. The method according to claim 7, wherein the injected thermally conductive material is left to solidify. 9. The method of claim 8, further comprising alternating pressure grouting and re-excavation of the bottom area to loosen the bottom area and create additional entry passages. 10. A method according to claim 7, characterized in that a casing with a closed bottom is inserted as a supply pipe for the heat transfer medium and the casing is thermally bonded to the heat-conducting material. (11) said casing against a base rock onto which a thermally conductive material has been injected, preferably by means of a sealing compound comprising cement and/or silica containing iron sanding powder or copper whiskers or copper fibers; 11. The method according to claim 10, characterized in that: 12. The method according to claim 10, characterized in that an inner tube as a return tube for the heat transfer medium is inserted into the supply tube. (13) (a) at least one shaft formed within the earth and having a bottom region; (b) located in said bottom region of the shaft and extending into the bedrock; (c) a thermally conductive material extensively filling said entry passage; and (d) supplying a heat transfer medium from the ground surface to said bottom area. (e) at least one of the supply pipe and the return pipe is configured to supply the thermally conductive material with respect to the thermally conductive material within at least the bottom region of the shaft; A geothermal plant characterized by being closely exposed. (14) The thermally conductive substance contains the following substances: (a) silica gel; and (b) finely ground metal powder, preferably consisting of silver and/or copper and/or aluminum powder; Claim 1 characterized in that at least one fine piece is included.
3. The geothermal plant described in 3. (15) (a) a closed-ended casing tube is thermally bonded to the bottom region of the shaft; and (b) the casing tube is thermally bonded to the bottom region of the shaft;
14. The geothermal plant of claim 13, wherein the geothermal plant is interconnected in close thermal contact with the thermally conductive material.